Process of treating waste magnesium monosulphite cooking liquor



- I UNIT-ED sraras Para VIGGO DREWSEN, OF IJARCHMONT, NEW

Patented Nov. 9, 1926.

q 1.665.929 NT ,ors ca.

YORK, AssIeNoa r wns'r vInGINIa PULP AND PAPER COMPANY OF NEW YORK, N. Y., A CORPORATION. OF IDELAWABE. i

PROCESS OF TREATING W ASTE MAGNESIUM MONOSULPHITE COOKING LIQUOR.

This application is a division of my copending application 'Serial 4 No. 549,197, filed April 3, 1922, 011 which U. S. Patent No. 1,549,189 was issued tome on August-11,1925, as a partial continuation of my copending application Serial No. 397,484,

" filed July 19, 1920,011 which application I latent No. 1,511,664 for a process of making fiber paper, etc.

was issued to me October 10, 1924.

This invention relates especially to processes of treating the waste monosulphite cooking liquors which are produced in the .digestlon of straw, corn stalks, wood, and

other fibrous material, for the production of paper pulp etc. so as to recover the valu able inorganic constituents of such liquors and prepare the cooking v liquors for. reuse in fibre digestionj The waste magnesium monosulphite liquor from the digester, preferably after precipitating out with calcium salts any sulphates or sulphites in the waste liquor, may be treated and preferably boiled .with slaked dolomite'lime so that the calcium component thereof precipitates the magnesium hydroxide which has been held in solution in various organic combinations in the waste liquor together with the mag nesia of the dolomite lime which may be removed by filter pressing. This precipitated magnesium hydroxide may be transformed into the monosulphite in various ways as by treating it with sulphur dioxide which may be percolated through liquor containing the magnesium hydroxide in suspension so that magnesium monosulphite may be formed for use in cooking the raw fibre, as, more specifically described and claimed in my afore:

said copending divisional application. According to the present process, however, the

unfied by calcining the'same to eliminate t ere from any'traces of drganic material, and the precipitated magnesium hydroxide is resulting magnesia may be treated while suspended in water with carbon dioxide under pressure. so as to produce magnesium bicarbonate whlch goes into solution. This solution may then betreated with sulphur dioxide or with magnesium bisulphite in proper proportions so asto form the desired magnesium monosulphite while concentrated carbon dioxide is simultaneously produced. which can be used inthe preoe No Drawing. Original application filed April 3, 1 22; Serial NJ. 549,197. Divided and thisa pplication filed December'17, 1924. Serial No. 756,615.

In commercially operating this process, the waste magnesium monosulphite liquorv from the raw fibrous material may advantageously have the sulphates and also .sulphites remaining therein from the original cooking liquor removed by precipitating out with any suitable calcium salts. For this purpose thewaste liquor from this recovery process containing v waste calcium organic compounds such as calcium 1i 0- sulphonate may be added andstirred into the waste liquor received from the digester so long continues. inarily 'removes these sulphates and sulphites which might otherwise contaminate the precipitated magnesium hydroxide formed in the liquor. This purified waste as a substantial calcium precipitate By 'filter pressing, thisprelimdigester. liquor may then be treated withabove indicated. This magnesia is prefer-- ably purified by calcining to eliminate any traces of combined organic material, and then it may be dissolved by carbon dioxide treatment under pressure to produce the acid magnesium carbonate or bicarbonate of magnesium. This solution may advantageously be filter-pressed which thus removes any silica or other insoluble material; and

the, solution may then'be treated with magnesium acid sulphite WlllCh produces the normal sulphite of magnesia and liberates the magnesium concentrated carbon dioxide which may be reused in the other step ofthe process to the extent necessary, and the surplus sold.

A surplus of magnesia is also produced in. this process which can be disposed of so as to help pa for the primary raw treating materials, olomite and sul ur or pyrites.

This invention has been escribed in connection with a number of illustrative ma,

terials, proportions, conditions, arrange-f ments and orders of steps,to the details of which disclosure the invention is not of toe limitedysinoe what is claimed as new and what is desired to be secured by Letters Patent isset forth in the appended claims.

I claim: l, The process of treating the Waste magnesium monosulphite treating liquor pro- 'material, which comprisesboiling the treating liquor with slaked lime to precipitate magnesium hydroxide, filtering out the precipitate and dissolving'the same in carbondioxide solution under pressure, and treating the resulting magnesium bicarbonate solution with magnesium acid-.sulphite to produce magnesium monosulphite for re use as such treating liquor.

3. "The process of treating the waste magnesium monosulphite treating liquor from the digestion ofvegetablc fibrous material, which comprises combining with the treating liquor slaked dolomite lime containing sufficient calcium hydroxide to substantially precipitate the magnesium hydroxide from said treating liquor, filtering out and calcining the precipitate and dissolving the same in carbon-dioxide solution under pressure to itorm magnesium bicarbonate solution, treating said solution with-materialcomprising available sulphur dioxide and forming magnesium monosulphite ;therefrom.

4:. The process of treating the waste magnesium monosulphite treating liquor from the digestion of vegetable fibrous material,

which comprises combining with the treating liquor slaked lime containing sufiicient calcium hydroxide to, substantially precipitate the magnesium hydroxide from said treating liquor, calcining. the. .precipitate and-dissolving the same in carbon-dioxide" solution to form magnesium bicarbonate solution, treating saidsolution with material' comprising available sulphur dioxide and forming-magnesium monosulphite therefrom.

5. The process of treatin the waste magnesium monosulphitetreatmg liquor the digestion of vegetable fibrous material,

which comprises combining with the treat ing liquor slaked dolomitic lime and precipitating magnesium hydroxide from said treating liquor, calcining theprecipitate and dlssolvmg the same 1n carbon-dioxide solutionunder pressure to form magneslum blcarbonate solution and forming magnesium monosulphite therefrom. i

6. The process of treatingthewaste magnesium monosulphite treating liquor from the digestion of vegetable fibrous material, which comprises combining with the treating liquor slaked lime and precipitating.

magnesium hydroxide from said treating liquor, calcining the precipitate and dis- I solving the same to form magnesium bicarbonate solution and forming magnesium monosulphite therefrom;

, 7. The process of treatin the waste magnesium monosulphite treatmg liquor produced in the digestion of vegetable fibrous material, which comprises removing sulphatesor sulphites from the treating liquor,'reacting on the purified treating liquor with slaked lime to precipitate magneslum hydroxide from said treating liquor, dissolving the precipitate -in carbon-dioxide solution under pressure, and filtering and treating the resulting magnesium bicarbonate solution with magnesium acid sulphite to produce magnesium monosulphite for re; use as such treating liquor. A

8. The process of treating the waste magnesium monosulphite treating liquor produced in the digestion of vegetable fibrous materiai, which comprises removing the sulphates or sulphitesfrom the treating liquor,

reacting on the purified treating liquor with slaked lime to precipitate magnesium hydroxide from said treating liquor, dissolving the precipitate in carbon-dioxide solution and treating the resulting magnesium, bicarbonate solution to produce magnesium monosulphite for reuse as such treating.

liquor.

9- Theprocess of treating the waste mag- 1185111111 monosulphite treating liquor produced in'the digestion of vegetable fibrous materiah which comprises removing the sulphates or sulphites -from the treating liquor, reacting on the urified treating liquor with slaked; dolomit1c lime to recipitate magnesium hydroxide"fro m' said treating liquor, dissolving the precipitate in carbondioxide solution and treating the resulting,

magnesium bicarbonate solution to produce magnesium monosulphite for-reuse as such weeo 'naawsnn'.

treating liquor. 

